In the manufacturing of LCD displays, it is necessary to bond glass components to one another. The bonded glass components may be used in the formation of LCD stacks, glass front plates, lamination of touch panels, and other glass features found in LCD displays. Generally, glass components are bonded using an optical adhesive interposed between the glass components. Traditional adhesives and bonding processes are time consuming and are subject to problems/defects resulting in a display unfit for consumer use.
Traditionally, adhesives for display glass components have a two part design. A first part being a resin and a second part being a catalyst. The first and second parts are then mixed together. As the first and second parts of the adhesive contact one another they undergo a reaction and begin to cure. This immediate curing significantly reduces the workable time of the mixture. The short workable time of the material may lead to various defects in the display.
One such problem with traditional methods is the formation of air bubbles in the adhesive. As the optical adhesive is interposed between two glass components, the display would be ruined if bubbles were present. Another problem that may occur during the bonding process is known as the halo effect or window framing. The halo effect may be caused by using an insufficient amount of adhesive to maintain glass component coverage during the curing phase. As the optical adhesive cures and experiences shrinking, the adhesive may pull away from the edges of the bonded glass components, resulting in both mechanical and optical failures.
Insufficient amounts of adhesive could also lead to mechanical separation of the glass components. In addition, the immediate curing may not allow for the glass components to be readjusted after coming into contact with the adhesive. When defects in the finally assembled glass are present, the only options left to manufacturers are to either dispose of the rejected components or spend large amounts of time manually removing the adhesive from the glass components. These problems are now magnified as the size of LCD displays are becoming larger and larger which necessitate the need for larger, more expensive glass components.
To eliminate some of these problems ultraviolet (hereinafter “UV”) light cured adhesives have been used. UV cured adhesives may include one or two parts. The adhesive may be applied to the glass component for bonding. After the adhesive is applied, it is cured by using a UV light source to direct UV toward the adhesive. Although these adhesives may provide benefits over traditional mix cured adhesives, some problems still exist. One such problem is the increased cost of production due to the need to maintain the UV light during the curing phase. Another problem is that display features such as grid heaters, anti-reflective layers, or other devices may prevent the UV light from reaching the entire adhesive. The result may be that portions of the adhesive are not cured properly and thus weaken the bond. This weakness may result in increased mechanical separation and image distortion as a result of the uncured adhesive.
These and other problems related to traditional optical display adhesives may be eliminated through the use of the exemplary embodiments described herein. In one exemplary embodiment an encapsulated two part photo-initiated adhesive may be used to bond glass components of a display. The adhesive may comprise a first part being a resin (hereinafter “part A”, “resin portions”, or “resin”) and a second part being a catalyst (hereinafter “part B”, “catalyst portions”, or “catalyst”) (collectively “components”). As the adhesive resulting from the combination of resin and catalyst may be used to optically bond glass components of a display, the adhesive would preferably be substantially transparent and provide minimal image distortion. Platinum catalysts have been found to provide a suitable optical adhesive. The curing process of platinum group catalysts may be found in U.S. Pat. No. 5,548,038 filed on Mar. 14, 1995; and U.S. Pat. No. 5,661,210 filed on Sep. 25, 1996, incorporated herein by reference in their entirety.
To prevent premature contact or reaction between parts A and B, each part (or one of the parts) may be encapsulated. The term ‘encapsulated’ is used herein to define at least a portion of a mixture which is substantially surrounded by an envelope to prevent the portion from prematurely mixing with other portions. The encapsulated parts A and B may then be mixed together creating a viscose material. The mixture may then be applied to a glass component of a display for bonding. After a sufficient amount of the encapsulated mixture has been applied to the glass component, the mixture is exposed to a UV light source. Upon exposure to UV light, the capsules surrounding parts A and B release the resin and catalyst. Parts A and B then proceed to mix together creating an adhesive. After the adhesive has been formed it may then begin to cure. Another glass component may then be placed on the adhesive, such that the adhesive is interposed between two glass components. The adhesive may then be allowed to cure forming the bond between the glass components.
The glass components may be any component used in an electronic display or any other type of glass components which may require optical bonding. In an exemplary embodiment, the adhesive may cure simply at room temperature. In some embodiments, it may be desirable to cure the adhesive at an elevated temperature. The UV light source may be required only to release the encapsulated portions and may not be required for the actual curing of the mixed adhesive. Once the adhesive is cured, the remnants of the encapsulating element may be present.
In another exemplary embodiment, part A may be encapsulated and mixed with part B. In still other exemplary embodiment, part B may be encapsulated and mixed with part A. As the capsule shields do not react with either part A or part B, the parts are not in contact, thus not forming the adhesive. In other exemplary embodiments, the adhesive formed by parts A and B may be able to penetrate the capsule shield. In this manner, capsules not exposed to the UV light may still release their contents, and the resin or catalyst contained therein may be incorporated into the adhesive.
The described exemplary embodiments provide several advantages over traditional optical adhesives. The ability to premix the resin and the catalyst without adhesive formation increases the production time by eliminating the mixing process. In addition, the ability of the adhesive to release the contents of adjacent capsules allows a more uniform bond between the glass components.
To further ensure a lack of defects, the adhesives disclosed herein can be applied using an exemplary process. In one exemplary embodiment of this process, a first glass component having a frame is provided, the frame being in contact with the first glass component. A sealant is used to seal the edge of the frame and the first glass component. This sealant is then allowed to cure. A barrier coat is applied over the sealant. The barrier coat is then allowed to cure. The encapsulated mixture is poured over the entirety on the first glass component and frame. A second glass component is placed on the frame with one end still elevated over the first glass component. The second glass component is slowly lowered until the previously elevated edge rests on the frame, resulting in a layer of the encapsulated mixture interposed between the second glass layer and the first glass layer and the frame. The capsules may then be broken down, the components mix to create the adhesive, and the adhesive is cured. Alternatively, the capsules may be broken down prior to placing the second glass component against the frame.
In another exemplary embodiment, the barrier coat step is removed and the encapsulated mixture is poured directly onto the first glass component, sealant, and the frame. In still another exemplary embodiment, an edge of the second glass component is placed at the intersection of the first glass component and the frame, still having an edge elevated above the first glass component. The second glass component is slowly lowered until the previously elevated edge rests at the intersection of the first glass component and the frame, resulting in a layer of the encapsulated mixture interposed between the second glass layer and the first glass layer. The capsules may then be broken down, the components mix to create the adhesive, and the adhesive is cured. Alternatively, the capsules may be broken down prior to placing the second glass component against the frame.
Further features of the exemplary embodiments will be described or will become apparent in the course of the following detailed description.